WASHINGTON (Reuters) — American children and teens are growing ever-fatter tummies, a bad sign that means they are at even more risk of heart disease and diabetes, US researchers reported yesterday.They found that the belly fat of children and teenagers had increased by more than 65 percent since the 1990s — directly in line with rising obesity rates.

But belly fat is more dangerous than general weight gain, because abdominal and visceral fat — found surrounding the internal organs — is more clearly and strongly linked with disease than general body fat.

Dr. Chaoyang Li of the Centers for Disease Control and Prevention, Dr. Stephen Cook of the University of Rochester School of Medicine and Dentistry in New York and colleagues examined data from several national surveys of health and fitness taken by the federal government.

They found that 10.5 percent of boys and girls had too much abdominal fat in 1999, as measured by waist circumference. This grew to 17.4 percent of boys and 17.8 percent of girls in 2004, they reported in the journal Paediatrics.

"Those increases only grow more alarming as you tease out specific age groups over longer periods of time," Cook said in a statement.

"For example, between the 1988-1994 data and the 1999-2004 data, the largest relative increase in the prevalence of abdominal obesity occurred among two- to five-year old boys — 84 percent — and 18- to 19-year-old girls — 126 percent."

Many studies have shown that measuring waist circumference can be a shortcut to determining if someone is unhealthily overweight — a better predictor than body mass index, which is a calculation of height to weight.

But it is not routinely done in doctors' offices.

Catching unhealthy body fat early can help people change their habits before any permanent damage is done, the researchers said.

"Kids, teens and adults who have early stages of atherosclerosis in their arteries can have a healthy cardiovascular system again," Cook said in a statement.

"Older adults who have plaque build-up have a much harder battle, especially if the plaque has calcified."